1. Field of the Invention
The invention relates generally to biometric techniques. More specifically, the invention relates to iris-based biometric techniques.
2. Description of the Related Art
Iris based biometric techniques are useful for recognition, verification, or tracking of individuals. Iris based biometric methods can provide high accuracy identification and other functions with relatively low system cost. Because of the availability of very efficient indexing techniques, iris-based biometrics can also be used when a large number of people must be screened and rapidly matched to a database of millions of individuals.
However, the widespread use of iris-based biometrics has been limited by the conditions imposed by the requirement that high resolution, high contrast images of the iris be obtained. This requirement was only met reliably by the careful positioning of a single, cooperative, stationary subject within the limited field of view of a suitable illumination and image capture device. Typical existing systems limit this capture volume to a small region of space within a few 10's of centimeters of the sensor. For example, the LG3000 system manufactured by LG Electronics requires a subject to remain stationary for 3-10 seconds at standoff distance of roughly 10 cm and provides a capture volume of roughly 10×2×2 cm or 0.04 liters. These limitations are workable in constrained settings such as security checkpoints, bank teller machines, or information system access points, but severely limit the applicability of iris biometrics in minimally constrained settings, such as screening in airports, subway systems, or at entrances to otherwise uncontrolled buildings or facilities.
In designing a practical iris-based biometric system having a large standoff distance, many variables must be addressed including the standoff distance for both the camera and illumination source, the iris illumination power (pulsed and continuous), the lens focal length, the capture volume, and so on. To design a system to fulfill specific design parameters for a given minimally constrained environment for the system, extensive trial and error “tuning” is required. Such trial and error tuning is time consuming and costly.
Therefore, there is a need in the art for a method and apparatus for designing iris-based biometric systems for use in minimally constrained settings.